mybatis自定义TypeHandler实现list转string

参考Mybatis实现自定义TypeHandler

1. 创建项目

完整的pom.xml文件如下

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.2.6.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.example</groupId>
    <artifactId>mybatis</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>mybatis</name>
    <description>Demo project for Spring Boot</description>

    <properties>
        <java.version>1.8</java.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.mybatis.spring.boot</groupId>
            <artifactId>mybatis-spring-boot-starter</artifactId>
            <version>2.1.2</version>
        </dependency>
        <!--spring-boot-starter-jdbc自动配置-->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-jdbc</artifactId>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <scope>runtime</scope>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
            <exclusions>
                <exclusion>
                    <groupId>org.junit.vintage</groupId>
                    <artifactId>junit-vintage-engine</artifactId>
                </exclusion>
            </exclusions>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

</project>

2. 配置application.yml

server:
  port: 8083
spring:
  datasource:
    url: jdbc:mysql://localhost:3306/test?useUnicode=true&characterEncoding=utf8&serverTimezone=Asia/Shanghai
    username: root
    password: 123456
    driver-class-name: com.mysql.cj.jdbc.Driver

3. 编写User pojo

@Data
public class User {
    private Integer id;
    private String name;
    private Integer age;
    private List<String> hobbies;
}

4. 编写控制器,service,mapper

@RestController
public class UserController {
    @Autowired
    UserService userService;

    @GetMapping("/users")
    private List<User> getAllUser(){
        return userService.getAllUser();
    }

    @PostMapping("/users")
    private Integer addUser(@RequestBody User user){
        return userService.addUser(user);
    }
}

@Service
public class UserService {
    @Autowired
    UserMapper userMapper;

    public List<User> getAllUser() {
        return userMapper.getAllUser();
    }

    public Integer addUser(User user) {
        return userMapper.addUser(user);
    }
}

@Component
public interface UserMapper {

    @Results({
            @Result(column = "id", property = "id"),
            @Result(column = "name", property = "name"),
            @Result(column = "age", property = "age"),
            @Result(column = "hobby", property = "hobbies" ,typeHandler= HobbyTypehandler.class),
    })
    @Select("select * from user")
    List<User> getAllUser();

    @Insert("insert into user " +
            "(name, age, hobby) " +
            "values (#{user.name}, #{user.age},"
            + "#{user.hobbies, typeHandler=com.example.mybatis.typeHandler.HobbyTypehandler})")
    @Options(useGeneratedKeys=true, keyProperty="id", keyColumn="id")
    Integer addUser(@Param("user") User user);
}

5. 编写自定义Typehandler

@Component
public class HobbyTypehandler implements TypeHandler<List<String>> {
    @Override
    public void setParameter(PreparedStatement preparedStatement, int i, List<String> strings, JdbcType jdbcType) throws SQLException {
        StringBuffer sb = new StringBuffer();
        for (String s : strings) {
            sb.append(s).append(",");
        }
        preparedStatement.setString(i, sb.toString().substring(0, sb.toString().length() - 1));
    }

    @Override
    public List<String> getResult(ResultSet resultSet, String s) throws SQLException {
        String[] arr = resultSet.getString(s).split(",");
        return Arrays.asList(arr);
    }

    @Override
    public List<String> getResult(ResultSet resultSet, int i) throws SQLException {
        String[] arr = resultSet.getString(i).split(",");
        return Arrays.asList(arr);
    }

    @Override
    public List<String> getResult(CallableStatement callableStatement, int i) throws SQLException {
        String[] arr = callableStatement.getString(i).split(",");
        return Arrays.asList(arr);
    }
}

6. 编写启动类

@SpringBootApplication
@MapperScan("com.example.mybatis.mapper")
public class MybatisApplication {

    public static void main(String[] args) {
        SpringApplication.run(MybatisApplication.class, args);
    }

}

7. mysql 表结构

CREATE TABLE `user` (
  `id` int(10) unsigned NOT NULL AUTO_INCREMENT,
  `name` varchar(255) DEFAULT NULL,
  `age` int(6) DEFAULT NULL,
  `hobby` varchar(255) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=6 DEFAULT CHARSET=utf8;

8. 测试

9. 代码

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